Effects of feeding lubabegron on gas emissions,growth performance,and carcass characteristics of beef cattle housed in small-pen environmentally monitored enclosures during the last 3 mo of the finishing period

The development of technologies that promote environmental stewardship while maintaining or improving the efficiency of food animal production is essential to the sustainability of producing a food supply to meet the demands of a growing population. As such, Elanco (Greenfield, IN) pursued an environmental indication for a selective β-modulator (lubabegron; LUB). LUB was recently approved by the United States Food and Drug Administration (FDA) to be fed to feedlot cattle during the last 14 to 91 d of the feeding period for reductions in gas emissions/kg of unshrunk final BW and HCW. A 4 × 2 factorial arrangement of treatments was used with the factors of dose (0.0, 1.38, 5.5, or 22.0 mg·kg⁻¹ DM basis) and sex (steers or heifers). Three 91-d cycles were conducted (112 cattle/cycle) with each dose × sex combination being represented by a single cattle pen enclosure (CPE; 14 cattle/CPE) resulting in a total of 168 steers and 168 heifers (n = 6 replicates/dose). There were no interactions observed between dose and sex for any variable measured in the study (P ≥ 0.063). Five gases were evaluated for all pens based on CPE concentrations relative to ambient air: NH₃, CH₄, N₂O, H₂S, and CO₂. Cumulative NH₃ gas emissions were reduced by feeding cattle 5.5 and 22.0 mg·kg⁻¹ LUB (P ≤ 0.023) and tended (P = 0.076) to be lower for the cattle fed 1.38 mg·kg⁻¹ LUB compared with the negative controls (CON). The cumulative NH₃ gas emission reductions of 960 to 1032 g, coupled with HCW increases (P ≤ 0.019) of 15 to 16 kg for all LUB doses vs. CON, led to reductions in NH₃ gas emissions/kg HCW for all three LUB treatments (P ≤ 0.004). Similar to HCW, reductions in NH₃ gas emissions/kg of unshrunk final BW were observed for all LUB doses (P ≤ 0.009) and were attributable to both decreases in NH₃ gas emissions and numerical increases in BW. Dose had no effect on cumulative emissions or emissions standardized by BW or HCW for the other four gases (P ≥ 0.268). LUB is a novel tool to reduce emissions of NH₃ gas per kilogram of unshrunk live BW and hot carcass weight.